1. Field of the Invention
The invention relates to a screw conveyor having a function of feeding sludge, food wastes, wood chips and so on in a predetermined direction.
2. Description of the Related Art
There have been suggested a lot of screw conveyors and apparatuses including screw conveyors therein. In general, a screw conveyor includes rotational shafts having spiral blades on an outer surface thereof, and feeds an object in a predetermined direction by rotating the rotational shafts.
FIG. 9 is a side view of the screw conveyor suggested in Japanese Patent Application Publication No. 2002-240923, and FIG. 10 is a cross-sectional view of the screw conveyor.
As illustrated in FIGS. 9 and 10, the illustrated screw conveyor 200 includes two shafts 202 having spiral blades 201 on an outer surface thereof and being in parallel with each other. The screw conveyor 200 has a function of feeding an object in an axial direction of the shafts 202 by rotating the shafts 202.
FIG. 11 is a side view of the screw conveyor suggested in Japanese Patent Application Publication No. 2008-39350, and FIG. 12 is a cross-sectional view of the screw conveyor.
As illustrated in FIGS. 11 and 12, the illustrated screw conveyor 300 includes two shafts 302 having spiral blades 301 on an outer surface thereof and being in parallel with each other. The screw conveyor 300 has a function of feeding an object in an axial direction of the shafts 302 by rotating the shafts 302.
The conventional screw conveyors 200 and 300 can feed an object without fail, if the object is solid and has low moisture content. However, when the conventional screw conveyors 200 and 300 have to feed an object having a high moisture content and/or an object having a high viscosity, such as sludge or food wastes, the object is often stuck on the blades 201 and 301 formed on outer surfaces of the shafts 202 and 302, and an area between the blades 201 and 301 is often clogged, resulting in that the object cannot be scraped off from the blades 201 and 301.
Under such circumstances, it is unavoidable that the blades 201 and 301 cannot feed an object sufficiently, or a high load exerts on a motor which rotates the shafts 202 and 302. Consequently, after stopping rotation of the shafts 202 and 302, the blades 201 and 301 have to be cleaned, resulting in significant decrease in working efficiency.